Zipper tape and packing bag with zipper tape

ABSTRACT

A thick portion is formed thick at an end of a female belt-like base near a containing space. To the thick portion near the containing space, a cut portion thinner than the female belt-like base is provided. To the cut portion near the containing space, a seal base that is thicker than the female belt-like base and is sealed to an inner surface of a bag body to which a male belt-like base is attached, is provided. Seal strength of the thick portion to the inner surface is lower than that of the seal base. The cut portion is provided to have a lower seal strength than that of the seal base. An area surrounded by the thick portion, the cut portion, the seal base and the inner surface becomes hermetically sealed. Even when external pressure is applied on the bag body, damages to the cut portion can be prevented.

TECHNICAL FIELD

The present invention relates to a zipper tape and a packaging bagprovided with the zipper tape.

BACKGROUND ART

There has typically been known a packaging bag with a zipper tape(hereinafter, occasionally abbreviated as a packaging bag) provided bybonding the zipper tape to an inner surface of the bag body. When such apackaging bag is filled with powdery substances and liquids as contents,the contents may leak toward a top seal beyond the zipper tape duringtransportation. Accordingly, a zipper tape with a separating structureprovided between the zipper tape and the contents and a packaging bagwith the zipper tape have been known for preventing leakage of thecontents (see, for instance, Patent Literatures 1 to 3).

The separating structure provided in the zipper tape is exemplified by acut portion, a part of which can be easily cut, and a seal that iseasily peelable from an inner surface of a bag body. In opening thepackaging bag, the cut portion is cut or peeled to take out thecontents.

Patent Literature 1 discloses a packaging bag including a wide seal baseprovided to a belt-like base of a male member near the contents. Theseal base includes a linear cut portion. The packaging bag is sealed bythe linear cut portion being bonded to an end of a belt-like base of afemale member. The linear cut portion is cut by a force in opening thezipper tape, thereby opening the packaging bag.

Patent Literature 2 (e.g., FIG. 10) discloses that a thin and linear cutportion is provided in a belt-like base of a male member near thecontents and the cut portion is cut to open a packaging bag.

Patent Literature 3 discloses that a connecting portion is provided as acut portion by connecting ends of non-opening-side-flanges of a malemember and a female member of a joint to each other and the connectingportion is cut to open the packaging bag. Patent Literature 3 alsodiscloses that a protrusion having a triangular cross section is formedon each of the ends of the male member and the female member, therebyallowing a stress to concentrate on the cut portion.

CITATION LIST Patent Literature(s)

-   Patent Literature 1 JP-A-2008-24324-   Patent Literature 2 International Publication No. WO2004/050487-   Patent Literature 3 JP-A-2006-51987

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In Patent Literatures 1 and 2, since the cut portion is linearly formed,when sealing the belt-like bases or the seal base of the male and thefemale members to the inner surface of the bag body, it is difficult toposition the seal base and the cut portion at a right place.Accordingly, the cut portion may be directly bonded to the inner surfaceof the bag body, or the belt-like base and the seal base may be bondedto each other. In such a case, cuttability of the cut portion may beimpaired.

In such a structure as disclosed in Patent Literature 3, unless at leastone of the protrusions is fixed to a bag body film, a sufficient forcecannot be applied on the cut portion to open the bag. Accordingly, itmay be difficult to cut the cut portion.

An object of the invention is to provide an easily openable andfavorably sealable zipper tape and a packaging bag with the zipper tape.

Means for Solving the Problems

According to an aspect of the invention, a zipper tape includes: a pairof a male member and a female member including: an engagement portionthat is engageable and disengageable and defines a containing spaceinside a bag body; and belt-like bases that are continuously connectedto the engagement portion and are bondable to an inner surface of thebag body, in which a first one of the belt-like bases includes: a thickportion that is formed thicker than the first one of the belt-like basesat an end near the containing space; a cut portion that is continuouslyconnected to the end of the thick portion near the containing space andis formed thinner than the first one of the belt-like bases; and a sealbase that is continuously connected to an end of the cut portion nearthe containing space, formed thicker than the first one of the belt-likebases, and attached to the inner surface of the bag body to which asecond one of the belt-like bases is attached, in which the thickportion is attached to the inner surface of the bag body to which thesecond one of the belt-like bases is attached by a strength lower than astrength for the seal base to be attached to the inner surface of thebag body, and the cut portion is provided in a form of a belt spacedaway from the inner surface of the bag body, the cut portion isolatingthe containing space from the outside and having a strength lower thanthe strength for the seal base to be attached to the inner surface ofthe bag body.

In the above aspect of the invention, it is preferable that the thickportion and the seal base are formed substantially in the samethickness.

In the above aspect of the invention, it is preferable that the thickportion is formed narrower toward the inner surface of the bag body.

In the above aspect of the invention, it is preferable that a surface ofthe thick portion and a surface of the seal base which face each otheracross the cut portion are substantially parallel to each other and aresubstantially orthogonal to the inner surface of the bag body to whichthe thick portion and the seal base are attached.

According to another aspect of the invention, a packaging bag with azipper tape includes: a bag body having an opening portion for defininga containing space; and the zipper tape according to any one of claims 1to 4, the zipper tape being provided on an inner surface of the bagbody.

According to the invention, even if external pressure or internalpressure of the bag is applied on the bag body with the zipper tapeattached and containing the contents in the containing space, since asubstantially hermetically sealed area is formed by the thick portion,the cut portion, the seal base and the inner surface of the bag body,the substantially hermetically sealed area works as a pressure bufferarea. Accordingly, even if the cut portion is configured to be easilycut in opening, the cut portion can be prevented from being stretched byexternal pressure or internal pressure of the bag to impair sealabilityfor separating the containing space from the outside, particularlywater-tightness. Consequently, both a favorable openability and asufficient sealability can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a packaging bag with a zipper tapeaccording to a first exemplary embodiment of the invention.

FIG. 2 is a cross section taken along the line II-II in FIG. 1 forshowing engagement of a male member and a female member.

FIG. 3 is an enlarged cross section of a seal base of the zipper tape inFIG. 2.

FIG. 4 is a cross section showing disengagement of the male member andthe female member in FIG. 2.

FIG. 5 is a cross section showing when a cut portion is cut to open thebag in FIG. 2.

FIG. 6 is a cross section showing how contents are sealed in thepackaging bag with the zipper tape.

FIG. 7 is a perspective view showing seal bars used for sealing thecontents.

FIG. 8 is a partially cut perspective view showing how the contents aresealed with the seal bars.

FIG. 9 is an enlarged perspective view showing an enlarged zipper tapein a packaging bag with a zipper tape according to a second exemplaryembodiment.

FIG. 10 is a cross section showing engagement of a male member and afemale member of a packaging bag with a zipper tape according to a thirdexemplary embodiment.

FIG. 11 is a cross section showing engagement of a male member and afemale member of a packaging bag with a zipper tape according to afourth exemplary embodiment.

FIG. 12 is a cross section showing engagement of a male member and afemale member of a packaging bag with a zipper tape according to a fifthexemplary embodiment.

DESCRIPTION OF EMBODIMENT(S) First Exemplary Embodiment

A packaging bag with a zipper tape according to a first exemplaryembodiment of the invention (hereinafter, occasionally referred tosimply as “a packaging bag”) will be described with reference todrawings.

The packaging bag of the invention is suitably filled with liquids ascontents. However, the packaging bag may be filled with powders, solidsor gel. Although a thick portion, a cut portion and a seal base areexemplarily provided to a female member, the thick portion, the cutportion and the seal base may be provided to a male member.

Arrangement of Packaging Bag with Zipper Tape

As shown in FIGS. 1 and 2, a packaging bag 1 of this exemplaryembodiment includes a bag body 10 provided by laying base films 11(packing material) one on the other and forming side seal bases 12 and atop seal base 13 on the periphery of the base films. A zipper tape 20includes a pair of a male member 21 and a female member 22 including anengagement portion 23. The male member 21 includes a male belt-likeportion 211. The female member 22 includes a female belt-like portion221. The male belt-like portion 211 and the female belt-like portion 221are continuously connected to the engagement portion 23. The zipper tape20 is attached to an inner surface 10A of an opening portion 14 of thebag body 10. The zipper tape 20 is sealed to the bag body 10 in a beltextending from one of the side seal bases 12 to the other of the sideseal bases 12. The engagement portion 23 of the zipper tape 20 defines acontaining space 15 in the packaging bag 1.

In FIGS. 1 to 3, after the contents (not shown) are put through a bottomof the bag body 10, the bottom side of the bag body 10 is sealed,whereby the packaging bag 1 is hermetically sealed.

In use, a user cuts the opening portion 14 to open the packaging bag 1,and reseals the packaging bag with the zipper tape 20.

As shown in the cross section in FIG. 2, the zipper tape 20 includes themale member 21 provided on one side and the female member 22 provided tothe other side to engage with the male member 21, the male and femalemembers 21 and 22 each formed of a thermoplastic resin and having abelt-like shape.

The male member 21 includes: the male belt-like base 211 sealed to thebag body 10; a head 212 shaped substantially in an arrowhead in crosssection; and a connecting portion 213 for connecting the male belt-likebase 211 and the head 212. The male belt-like base 211, the head 212 andthe connecting portion 213 are integrally formed.

Similarly to the male member 21, the female member 22 includes: thefemale belt-like base 221 sealed to the bag body 10; and a first hook222 and a second hook 223 that each have an arcuate cross section andare connected to the female belt-like base 221. The first hook 222 andthe second hook 223 face each other and are in a form of a groovedetachably engageable with the head 212 of the male member 21.

The male belt-like base 211 of the male member 21 includes: a basefacing surface 221A that is sealed to the inner surface 10A in a mannerto substantially face the inner surface 10A; and an engagement-portionformation surface 221B near the engagement portion 23 opposite to thebase facing surface 221A. The female belt-like base 221 of the femalemember 22 includes: a base facing surface 221A that is sealed to theinner surface 10A in a manner to substantially face the inner surface10A; and an engagement-portion formation surface 221B near theengagement portion 23 opposite to the base facing surface 221A.

The engagement portion 23 of the zipper tape 20 is provided by the head212 of the male member 21 and the first and second hooks 222, 223 of thefemale member 22. By engagement or disengagement of the engagementportion 23, the packaging bag 1 is sealed or opened.

As shown in FIGS. 2 and 3, the female belt-like base 221 integrallyformed with the female member 22 includes a thick portion 31, which isthicker than the female belt-like base 221, at an end 224 of the bagbody 10 near a containing space 15.

To an end of the thick portion 31 near the containing space 15, abelt-like cut portion 32, which is formed thinner than the thick portion31 and isolates the containing space 15 from the outside, is connected.

To an end of the cut portion 32 near the containing space 15, a sealbase 33, which is formed thicker than the female belt-like base 221 andis sealed to the inner surface 10A, is connected.

The thick portion 31 is formed thicker than the female belt-like base221 and projects from the engagement-portion formation surface 221Bwhile being formed in a belt from one side seal base 12 to the otherside seal base 12. The thick portion 31 is formed substantially in thesame thickness as that of the seal base 33.

A thickness of the thick portion 31 is preferably in a range of 250 μmto 550 μm, more preferably in a range of 350 μm to 450 μm. When thethickness of the thick portion 31 is less than 250 μm, a stress inopening the packaging bag 1 is difficult to concentrate on the cutportion 32. On the other hand, when the thickness of the thick portion31 is more than 550 μm, it is difficult to form the side seal base 12.

The thick portion 31 is formed narrower toward the inner surface 10A ofthe bag body 10, the inner surface 10A facing the engagement-portionformation surface 221B. In other words, the thick portion 31 is formedin a cross-sectionally trapezoidal shape, in which a width of the thickportion 31 becomes narrower toward its projecting end.

The thick portion 31 is sealed to the inner surface 10A through an endsurface 311 facing the inner surface 10A. Under such a sealed situation,an end surface 312 of the thick portion 31, to which the cut portion 32is connected, is formed substantially orthogonal to the inner surface10A. Seal strength of the thick portion 31 to the inner surface 10A islower than that of the seal base 33 to the inner surface 10A. The sealstrength of the thick portion 31 is adjusted by configuring the thickportion 31 to have a seal area smaller than a seal area of the seal base33 (a seal area of an adhesion portion 331A later described) through apartial seal portion 311A that is sealed in a dashed line in alongitudinal direction (a horizontal direction in FIG. 1) of the cutportion 32.

The thick portion 31 is formed at a distance of 0.5 mm or more betweenan outside edge of the end surface 311 and an end of the male belt-likebase 211 near the containing space 15. This is because, if the distanceis less than 0.5 mm, when the thick portion 31 is sealed to the innersurface 10A, the thick portion 31 and the male belt-like base 211 mayadhere to each other, so that a favorable opening feeling may not beobtained or the bag cannot be opened depending on the case. The thickportion 31 in a cross-sectionally trapezoidal shape is formed to have aninclined surface 313 such that the outer edge of the end surface 311 isspaced away from the male belt-like base 211. Accordingly, the thickportion 31 is prevented from adhering to the male belt-like base 211 insealing.

The cut portion 32 is formed in a belt extending from one of the sideseal bases 12 to the other of the side seal bases 12 and in a directionorthogonal to the end surface 312 of the thick portion 31 (a verticaldirection in FIG. 3). The cut portion 32 is formed to have a sealstrength lower than that of the seal base 33 to the inner surface 10A.In other words, the cut portion 32 is formed so as to be cut before theseal base 33 is peeled from the inner surface 10A of the bag body 10.Specifically, a thickness of the cut portion 32 is preferably in a rangeof 10 μm to 80 μm, more preferably in a range of 30 μm to 60 μm. Whenthe thickness of the cut portion 32 is less than 10 μm, the cut portion32 may be cut by external pressure when the packaging bag 1 is dropped.On the other hand, when the thickness of the cut portion 32 is more than80 μm, it may be difficult to cut the cut portion 32 by hand. It shouldbe noted that the strength of the cut portion 32 may not be adjustedsimply by setting the thickness of the entire cut portion 32 in theabove range. For instance, thin portions may be formed in the cutportion 32 at every predetermined distance between one of the side sealbases 12 and the other of the side seal bases 12.

A width of the cut portion 32, i.e., a dimension in a directionsubstantially orthogonal to a longitudinal direction of the zipper tape20 (i.e., the vertical direction in FIG. 3), is preferably in a range of0.3 mm to 1.5 mm, more preferably in a range of 0.8 mm to 1.2 mm. If thewidth of the cut portion 32 is less than 0.3 mm, when the zipper tape 20is sealed to the bag body 10, it may be difficult to position the cutportion 32 so as not to contact with the male belt-like base 211 of themale member 21 and the inner surface 10A. On the other hand, when thewidth of the cut portion 32 is more than 1.5 mm, the cut portion 32 maybe stretched in cutting to become difficult to cut.

The seal base 33 is formed in a belt having a cross-sectionallyrectangular shape extending from one of the side seal bases 12 to theother of the side seal bases 12.

A seal surface 331 of the seal base 33 which is sealed to the innersurface 10A is formed substantially flush with the end surface 311 ofthe thick portion 31 which is sealed to the inner surface 10A (see FIG.6). The seal surface 331 includes the adhesion portion 331A that isbonded to the inner surface 10A in a comb-shape pattern. As shown inFIG. 1, the adhesion portion 331A includes: a linear seal surface 331A1that is linearly sealed along the longitudinal direction (the horizontaldirection in FIG. 1) of the cut portion 32; and a plurality of end sealsurfaces 331A2 that are continuously formed with the linear seal surface331A1, to which an end surface 333 of the seal base 33 is sealed in adashed line. The linear seal surface 331A1 prevents leakage of thecontents and the plurality of end seal surfaces 331A2 allow the stressto concentrate on the cut portion 32.

The end surface 333 of the seal base 33, to which the cut portion 32 isconnected, is formed substantially parallel to the end surface 312 ofthe thick portion 31 facing the seal base 33 and substantiallyorthogonal to the inner surface 10A of the bag body 10.

The male member 21 of the zipper tape 20 of the exemplary embodiment canbe integrally formed by co-extrusion, where the head 212 and theconnecting portion 213 are continuously formed with the male belt-likebase 211. Similarly, the female member 22 can be integrally formed byco-extrusion, where the first hook 222 and the second hook 223 arecontinuously formed with the female belt-like base 221. When the zippertape 20 is formed by such co-extrusion, the zipper tape 20 can bemanufactured in a simplified process at low costs, and can be stablymanufactured in a continuous manner.

The male member 21 and the female member 22 of the zipper tape 20 may beformed of polyethylene and polypropylene and are preferably formed ofextension-resistant polypropylene. Specifically, thermoplastic resinssuch as homo-polypropylene, block-polypropylene, random polypropylene(RPP), propylene-ethylene-butene-1 random terpolymer andpolyolefin-based special flexible resins, and a mixture thereof areusable.

When random polypropylene (RPP) is used as the resin forming zipper tape20, a melt flow rate (MFR) of RPP is preferably from 0.5 to 20 g/10 min,particularly preferably from 1 to 15 g/10 min.

When the MFR of random polypropylene is less than 0.5 g/10 min,co-extrusion moldability of the engagement portion 23, which is formedcontinuously and integrally with the male belt-like base 211 and thefemale belt-like base 221, may be deteriorated. On the other hand, theMFR exceeding 20 g/10 min may cause ends of the first and second hooks222 and 223 of the female member 22 to be likely closed or may cause theconnecting portion 213 of the male member 21 to be likely tilted down,which may make it difficult to extrude the zipper tape 20 into apredetermined reopenable/resealable shape.

By sealing the zipper tape 20 to the base film 11 of the bag body 10 andforming the base film 11 into a bag, the packaging bag 1 as shown inFIG. 1 can be obtained.

While the base film 11 (packaging material) for forming the bag body 10is preferably a layered film in which a sealant layer 111 is layeredonto a base layer 112, the base film 11 may be a layered film in which alayered film layer (not shown) including layers of a gas barrier layer,a light-shielding layer and a strength-reinforcing layer is provided asa middle layer between the base layer 112 and the sealant layer 111,depending on a required performance.

Examples of the material for the base layer 112 are preferably abiaxially-oriented polypropylene film (OPP film), a biaxially-orientedpolyester film such as biaxially-oriented polyethylene terephthalatefilm (PET film) and biaxially-oriented polyethylene naphthalate film anda biaxially-oriented polyamide film such as nylon 6, nylon 66 and MXD6(poly-meta-xylylene adipamide). Depending on needs, various engineeringplastic films are also usable. One of the above may be used alone, or acombination of two or more of the above may be layered in use.

When the middle layer is a gas barrier layer, examples of the usablematerial for the middle layer are a film of saponified ethylene-vinylacetate copolymer (EVOH) or polyacrylonitrile (PAN), aluminum foil, adeposited layer of silica, alumina or aluminum and a coating layer ofPVDC.

When a deposited layer of silica, alumina or aluminum or a coating layerof PVDC is used, such a layer may be deposited or coated on the innersurface 10A of the bag body 10 of the base layer 112. Alternatively,such a layer may be preliminarily deposited or coated on anotherbiaxially-oriented nylon film (ONy film), biaxially-orientedpolyethylene terephthalate film (PET film) or biaxially-orientedpolypropylene film (OPP film), and the film may be layered on the middlelayer.

Among the above, aluminum foil and a deposited layer of aluminum, whichare opaque, can also serve as a light-shielding layer.

The layering of the base layer 112 and the film of the intermediatelayer can be conducted by a known dry lamination method or extrusionlamination method (sandwich lamination method).

For the sealant layer 111 (the innermost layer), polypropylene (CPP) andthe like are usable.

In order to layer the sealant layer 111, the above resins may be formedinto film and layered by a dry lamination method or extrusion laminationmethod. Alternatively, the above resins may be layered thereon byextrusion coating.

The packaging bag 1 according to this exemplary embodiment can be easilymanufactured with use of, for instance, a bag-making machine forthree-sided sealing and attaching a zipper tape.

Sealing conditions (temperature, pressure, etc.) in the manufacturingcan be properly determined in accordance with types of the resins forforming the zipper tape 20 and the base film 11 for forming the bag body10.

Opening Operation of Packaging Bag with Zipper Tape

Next, description will be made with reference to FIGS. 2, 4 and 5 on howthe packaging bag 1 according to this exemplary embodiment is opened.

FIG. 2 shows engagement of the male member 21 and the female member 22of the zipper tape 20. In this engagement, at a lower side of theengagement portion 23 (i.e., near the containing space 15) in FIG. 2,the adhesion portion 331A of the seal base 33 is sealed to the innersurface 10A of the bag body 10. This arrangement can maintainair-tightness and water-tightness of the bag, and liquid contents can bekept from infiltrating into a gap in the engagement portion 23 of thezipper tape 20, for instance, during transportation.

Next, when the contents are to be taken out from the packaging bag 1, asshown in FIG. 4, the opening portion 14 is cut to open the zipper tape20, thereby disengaging the engagement of the engagement portion 23. Byfurther opening an upper side (a side opposite to the containing space15) of the bag body 10, the thick portion 31 is peeled from the innersurface 10A of the bag body 10 by such an opening force, as shown inFIG. 5. By the opening force to further open the upper side of the bagbody 10, stretching force acts on the cut portion 32. At this time,since the end surface 333 of the seal base 33 near the cut portion 32 iskept orthogonal to the inner surface 10A of the bag body 10 by the endseal surfaces 331A2 of the adhesion portion 331A, the end surface 333 ofthe seal base 33 does not become loose from the inner surface 10A, sothat the stretching force efficiently acts on the cut portion 32. Thecut portion 32 is cut by the stretching force, so that the thick portion31 is separated from the seal base 33. Thus, the contents can be takenout from the inside of the packaging bag 1.

Manufacturing Instrument of Packaging Bag with Zipper Tape

Next, a manufacturing instrument of the packaging bag with the zippertape according to the first exemplary embodiment will be described withreference to FIGS. 6 to 8.

The manufacturing instrument used for manufacturing the packaging bag 1includes a bag-making section. FIG. 6 shows how the contents are sealedin a substantial part of the bag-making section.

In FIG. 6, the bag-making section includes: a tape adhesion section (notshown) that positions the zipper tape 20 fed from a tape feeder (notshown) between a pair of the base films 11 fed from a packaging materialfeeder (not shown) and heat-seals the zipper tape 20 to both of the basefilms 11; and a seal section that seals and weld-cuts the delivered basefilms 11 at a predetermined distance in a delivering direction of thebase films 11, i.e., at a distance corresponding to a dimension in awidth direction of the packaging bag 1, thereby forming the packagingbag 1.

The seal section includes a pair of seal bars 60 that are disposed toface each other with interposing the packaging bag 1 that is filled withcontents P while the zipper tape 20 is fastened.

The seal bars 60 are mutually approachable and separable. When the sealbars 60 are separated from each other, the packaging bag 1 containingthe contents P is held at a predetermined position. At this time, whenthe seal bars 60 approach each other, one of the seal bars 60 pressesthe seal base 33 via the base film 11, thereby forming the adhesionportion 331A on the seal base 33.

As shown in FIG. 7, the one of the seal bars 60 is provided withpressing protrusions 60A in the same continuous comb-shape as that ofthe adhesion portion 331A. As shown in FIG. 8, the adhesion portion 331Aof the seal base 33 is formed to have a predetermined width in the widthdirection of the bag body 10 and a comb-shape dented at a predetermineddistance in the longitudinal direction of the bag body 10. The adhesionportion 331A is sealed with the seal bars 60 in such a manner that endsof the pressing protrusions 60A reach the thick portion 31 across thecut portion 32.

In this exemplary embodiment, when the zipper tape 20 near thecontaining space 15 is sealed, the adhesion portion 331A is formable byusing the seal bars 60 provided with the pressing protrusions 60A havingthe same shape as the adhesion portion 331A. Thus, it is possible tomanufacture the packaging bag 1 in which the thick portion 31 is easilypeelable and the cut portion 32 is easily cuttable by the force appliedfor opening the zipper tape 20.

Advantages of First Exemplary Embodiment

With the above-described packaging bag 1, the following advantages canbe attained.

Specifically, in the first exemplary embodiment, the thick portion 31 isformed thick at the end 224 of the female belt-like base 221 near thecontaining space 15. To the thick portion 31 near the containing space15, the cut portion 32 thinner than the female belt-like base 221 isprovided. To the cut portion 32 near the containing space 15, the sealbase 33, which is thicker than the female belt-like base 221 and issealed to the inner surface 10A of the bag body 10 to which the malebelt-like base 211 is attached, is provided. The thick portion 31 isattached to the inner surface 10A to which the male belt-like base 211is attached by the seal strength lower than that of the seal base 33.The cut portion 32 is formed to have strength lower than the sealstrength of the seal base 33 and to be spaced away from the innersurface 10A of the bag body 10 and separate the containing space 15 fromthe outside in a form of a belt.

With this arrangement, an area surrounded by the thick portion 31, thecut portion 32, the seal base 33 and the inner surface 10A of the bagbody 10 becomes substantially hermetically sealed. Accordingly, even ifexternal pressure or internal pressure of the bag is applied on the bagbody 10 to which the zipper tape 20 is attached and which contains thecontents P in the containing space 15, the substantially hermeticallysealed area works as a buffer area of the pressure applied on a surfaceof the cut portion 32 near the containing space 15. With thisarrangement, even if the cut portion 32 is set to have a predeterminedstrength enough to be easily cut in opening, the cut portion 32 isprevented from being stretched by external pressure or internal pressureof the bag to be broken on next impact, or the cut portion 32 isprevented from occasionally having pinholes to damage sealability forseparating the containing space 15 from the outside, particularlywater-tightness. Consequently, according to this exemplary embodiment,it is avoidable to damage openability by forming the cut portion 32thick for improving sealability, thereby providing both a favorableopenability and a sufficient sealability.

Moreover, in the first exemplary embodiment, the thick portion 31 andthe seal base 33 are formed substantially in the same thickness.

With this arrangement, when the seal bars 60 heat-weld the thick portion31 and the seal base 33, the seal bars 60 come into contact with thethick portion 31 and the seal base 33 substantially at the same time,whereby a predetermined pressure is applied on the end surface 311 ofthe thick portion 31 and the seal surface 331 of the seal base 33, sothat the end surface 311 and the seal surface 331 can be bonded under apredetermined heat-welding condition.

In other words, if one of the end surface 311 and the seal surface 331is formed thicker than the other, the seal bars 60 need to be pressedharder in order to seal the other, so that the cut portion 32 may bedamaged by heat. If the thick portion 31 is formed thinner and is notappropriately sealed on the bag body 10, the cut portion 32 may bestretched to damage sealability when external pressure is applied on thebag body 10. On the other hand, if the thick portion 31 is formedthicker, the seal strength is increased to require a large force forpeeling the thick portion 31 from the bag body 10 in opening, so that anopening feeling may be impaired. If the seal bars 60 are formedcorresponding to different thicknesses for solving such disadvantages, ashape of the seal bars 60 becomes complicated to increase instrumentcosts and positioning of the seal bars 60 in sealing also becomescomplicated, so that the manufacturing efficiency of the packaging bag 1may not be improved.

For solving such disadvantages, according to the above arrangement ofthis exemplary embodiment, an arrangement in which the thick portion 31is sealable by the seal strength lower than that of the seal base 33 isprovided by a simple arrangement in which the thick portion 31 and theseal base 33 are formed substantially in the same thickness.

Moreover, in the first exemplary embodiment, the thick portion 31 isformed in a cross-sectionally trapezoidal shape, in which a width of thethick portion 31 becomes narrower toward the inner surface 10A of thebag body 10.

With this arrangement, in sheet-sealing, a seal depth is easilyadjustable, which makes it possible to set the seal conditions in abroad range.

For instance, when the thick portion 31 is formed in a cross-sectionallyinverse trapezoidal shape in which the width of the thick portion 31becomes wider toward the end surface 311 and the inclined surface 313 isinversely inclined, it is difficult to stably mold the thick portion 31to hinder improvement in productivity. Particularly, in across-sectionally inverse trapezoidal shape in which the end surface 312of the thick portion 31 approaches the seal base 33 toward the endsurface 311, resins flowed out in sealing may be bonded to the cutportion 32 or the seal base 33, so that an opening feeling may beimpaired.

In view of the above, according to the above arrangement of thisexemplary embodiment, an arrangement to provide a favorable openingfeeling can easily be manufactured by co-extrusion.

The cut portion 32 is formed in a belt extending in a directionorthogonal to the end surface 312 of the thick portion 31 (in thevertical direction in FIG. 3).

Accordingly, even when external pressure is applied on the bag body 10,the external pressure is substantially evenly applied on the entire cutportion 32, so that the cut portion 32 can be kept from being stretchedby partially receiving a high pressure, and decrease in water-tightnesscaused by generation of pinholes can be prevented.

Further, the surfaces of the thick portion 31 and the seal base 33 to besealed on the inner surface 10A of the bag body 10 are formedsubstantially flush with each other. The seal base 33 is designed tohave a higher seal strength higher than the thick portion 31.

Examples of methods to achieve the above arrangement include: sealingthe thick portion 31 and the seal base 33 from an outer surface of thebag body 10 using comb-shaped heat seal bars 60; forming the thickportion 31 using a non-compatible resin with the resin used in thesealant layer 111 of the bag body 10; and setting a melting point of theresin used for the thick portion 31 higher than a melting point of theresin used for the seal base 33. By using these methods, such designthat the seal base 33 is sealed by the seal strength higher than that ofthe thick portion 31 is reliably obtained, thereby easily providing anarrangement with a favorable openability and a sufficientwater-tightness.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the invention will be describedwith reference to the drawings.

FIG. 9 is an enlarged perspective view showing a vicinity of a seal baseof a zipper tape of a packaging bag according to the second exemplaryembodiment of the invention. It should be noted that, in the secondexemplary embodiment, description of an arrangement that is the same asor similar to the arrangement of the first exemplary embodiment isomitted or simplified.

A thick portion 41 of the second exemplary embodiment is provided byforming the thick portion 31 of the first exemplary embodiment into across-sectionally rectangular shape. The thick portion 41 includes tworibs 411 having a cross-sectionally triangular shape along alongitudinal direction of the cut portion 32 on a surface of the thickportion 41 facing the inner surface 10A of the bag body 10 to which themale belt-like base 211 is attached. The ribs 411 are preferably formedto have a predetermined height. Specifically, when the height is lessthan 5 μm, the rib is sealed up to an end surface of a base thereof,which means that formation of the ribs 411 is not necessary. When theheight is more than 300 μm, it is difficult to form the side seal bases12 in the packaging bag 1.

A thickness of the thick portion 41, which is defined as a dimensionfrom a bottom surface continuous to the female belt-like base 221 to atip end of the rib 411, is formed substantially the same as that of theseal base 33.

In the second exemplary embodiment, the seal base 33 is bonded to thebag body 10 with an arrangement in which the linear seal surface 331A1and the end seal surface 331A2 of the adhesion portion 331A in the firstexemplary embodiment are separated.

According to the second exemplary embodiment, since the ribs 411 to bebonded to the bag body 10 are provided, the seal strength is reducedbecause of decrease in seal area on the bag body 10, so that a largeforce is not required in opening and a favorable opening feeling can beprovided. Particularly, even when the thick portion 41 needs to bebonded to the bag body 10 all along the longitudinal direction of thecut portion 32 in order to more reliably prevent the cut portion 32 frombeing damaged by external pressure, the thick portion 41 can easily bebonded to the bag body 10 by a seal strength lower than that of the sealbase 33 and a favorable opening can be provided.

Moreover, even by the method of bonding the linear seal surface 331A1and the end seal surface 331A2 in the separate arrangement in the secondexemplary embodiment, similarly to the first exemplary embodiment, thestress appropriately concentrates on the cut portion 32 in opening,whereby the cut portion 32 can be cut and a favorable opening feelingcan be provided,

In the second exemplary embodiment, the ribs 411 are not limited to tworibs, but may be provided by a single rib or plural ribs. A shape ofeach of the ribs 411 is not only linear, but may be wavy or in a dashedline. The adhesion portion 331A of the seal base 33 may be bonded by anybonding method such as one in a comb-shape pattern of the firstexemplary embodiment.

Third Exemplary Embodiment

Next, a third exemplary embodiment of the invention will be describedwith reference to the drawings.

FIG. 10 is a cross-sectional view showing engagement of a male memberand a female member of a zipper tape in a packaging bag according to athird exemplary embodiment of the invention. Also in the third exemplaryembodiment, description of an arrangement that is the same as or similarto the arrangement of the above exemplary embodiments is omitted orsimplified.

According to the third exemplary embodiment, a cut portion 42 isprovided by forming the cut portion 32 of the second exemplaryembodiment in a plane on which the cut portion 42 intersects with theinner surface 10A of the bag body 10 facing the thick portion 41 and theseal base 33. In case external pressure is applied, in order to preventpressure concentration, it is preferable to provide a curved surface 421formed in a cross-sectionally arc at an acute connecting point betweenthe cut portion 42 and the seal base 33.

Also with this arrangement, similar to the second exemplary embodiment,a favorable opening feeling can be provided in opening and a favorablesealability can be obtained without causing such damage as the cutportion 42 is stretched even when external pressure is applied.

In the third exemplary embodiment, a direction in which the plane of thecut portion 42 is inclined is not limited to the above arrangement, butmay be an inverse direction. The cut portion 42 may be curved.

Fourth Exemplary Embodiment

Next, a fourth exemplary embodiment of the invention will be describedwith reference to the drawings.

FIG. 11 is a cross-sectional view showing engagement of a male memberand a female member of a zipper tape in a packaging bag according to afourth exemplary embodiment of the invention. Also in the fourthexemplary embodiment, description of an arrangement that is the same asor similar to the arrangement of the above exemplary embodiments isomitted or simplified.

According to the fourth exemplary embodiment, a cut portion 52 isprovided by forming the cut portion 42 of the second exemplaryembodiment thicker toward the thick portion 41.

With this arrangement, a position where the cut portion 52 is cut is aconnecting point (the thinnest point) between the cut portion 52 and theseal base 33, so that the products can be cut at the same cut positionand the opening feeling can be kept constant.

Fifth Exemplary Embodiment

Next, a fifth exemplary embodiment of the invention will be describedwith reference to the drawings.

FIG. 12 is a cross-sectional view showing engagement of a male memberand a female member of a zipper tape in a packaging bag according to afifth exemplary embodiment of the invention. Also in the fifth exemplaryembodiment, description of an arrangement that is the same as or similarto the arrangement of the above exemplary embodiments is omitted orsimplified.

In the fifth exemplary embodiment, the female belt-like base 221 of thefemale member 22 in the first exemplary embodiment includes an adhesionbase 24 at an end near the opening portion 14. The female belt-like base221 of the female member 22 is bonded to the inner surface 10A of thebag body 10 near the male member 21 with the engagement-portionformation surface 211B via the adhesion base 24. An opening tape 40 isattached between the adhesion base 24 and the male belt-like base 211 ofthe male member 21.

The base facing surface 221A opposite to the engagement-portionformation surface 211B is spaced away from the inner surface 10A of thebag body 10 at a predetermined distance. In other words, the femalebelt-like base 221 of the female member 22 is not sealed to the innersurface 10A of the bag body 10.

With this arrangement, the base facing surface 221A is spaced away fromthe inner surface 10A of the bag body 10 at a predetermined distance.Accordingly, the containing space 15 is enlarged, i.e., a so-called deadspace is decreased, so that the packaging bag 1 can contain largeramount of contents. Moreover, the internal pressure of the packaging bag1 is less likely to be applied on the cut portion 32, so that damage(e.g., the stretch) to the cut portion 32 can be prevented even when anexternal force (e.g., impact on the bag body 10 when dropped) isapplied.

Modification

The scope of the invention is not limited to the above-describedembodiments but also includes modifications and improvements as long asan object of the invention can be achieved.

The pair of seal bars 60 that are positioned to face each other with thepackaging bag 1 interposed therebetween are used for heat-welding thethick portion 31, 41 and the seal base 33, but an arrangement of theseal bars 60 is not limited to this. For instance, only a single sealbar may be provided on one side of the packaging bag 1, or plural sealbars may be provided on one side of the packaging bag 1.

The adhesion method for the thick portion 31, 41 and the seal base 33 isnot limited to the heat-welding method. Various methods such as anadhesion method using an adhesive or the like are applicable.

Other specific arrangements and shapes for carrying out the inventionmay be altered as long as an object of the invention is achieved.

EXAMPLES

The invention will further be described below with reference to examplesand a comparative example. It should be noted that the invention is notlimited to the contents of the examples and the like.

Example 1

With use of random polypropylene having MFR of 7 and a melting point of140 degrees C., the zipper tape shaped as shown in FIG. 2 wasmanufactured under the following conditions.

Arrangement of Zipper Tape

Thickness of Thick Portion: 300 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Arrangement of Bag Body

The base film forming the bag body, which was a film provided bydry-laminating the biaxially-oriented polyester film (thickness: 12 μm),the biaxially-oriented nylon film (thickness: 15 μm) and a castpolypropylene film (60 μm), was used for manufacturing a bag shown inFIG. 1.

As shown in FIG. 8, the seal base was sealed at a 1-mm width in thewidth direction of the bag (the direction orthogonal to the longitudinaldirection of the zipper tape) and was sealed by the comb-shaped seal barhaving a 1-mm width and 10-mm intervals in the longitudinal direction ofthe zipper tape in such a manner that ends of the comb reached the thickportion 31 across the cut portion 32.

An inner size of the bag from the seal of the seal base to the bottom ofthe containing space was set to be a width of 180 mm and a depth of 200mm.

Example 2

A packaging bag was manufactured in the same manner as that in Example 1except that the dimensions of the portions of the zipper tape in Example1 were replaced by the following.

Thickness of Thick Portion: 500 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Example 3

A packaging bag was manufactured in the same manner as that in Example 1except that the dimensions of the portions of the zipper tape in Example1 were replaced by the following.

Thickness of Thick Portion: 400 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Comparative 1

With use of random polypropylene having MFR of 7 and a melting point of140 degrees C., in the same shape as that of the zipper tape disclosedin JP-A-2008-24324 (FIG. 4), a zipper tape was manufactured under thefollowing conditions.

JP-A-2008-24324 (FIG. 4) discloses:

Thickness of Male Belt-like Base (reference numeral 321 in FIG. 4) ofMale Member and Female Belt-like Base (reference numeral 331 in FIG. 4)of Female Member: 150 μm

Seal Base (reference numeral 36): 150 μm

Thickness of Cut Portion (Linear Portion: reference numeral 35): 40 μm

Width of Cut Portion: 0.1 mm

The base film, which was a film provided by dry-laminating abiaxially-oriented polyester film (12 μm), a biaxially-oriented nylonfilm (15 μm) and a cast polypropylene film (60 μm), was used formanufacturing the bag shown in FIG. 2, similarly to Example 1.

Similarly to Example 1, as shown in FIG. 8, the seal base was sealed ata 1-mm width in the width direction of the bag and was sealed by thecomb-shaped seal bar having a 1-mm width and 10-mm intervals in thelongitudinal direction in such a manner that ends of the comb reachedthe belt-like base across the cut portion.

An inner size of the bag from the seal of the seal base to the bottom ofthe containing space was set to be a width of 180 mm and a depth of 200mm.

Evaluation

The packaging bags manufactured in Examples 1 to 3 and Comparative 1were evaluated according to the following method. The evaluation resultsare shown in Table 1.

Evaluation Method

(1) The cut portion was opened by hand.

A: easily openable

B: resistant to be opened, but openable

C: difficult to be opened

(2) Water of 400 ml was filled in the manufactured bag and the bag wassealed. The bag was dropped by N10 from a height of 1.2 m. It waschecked whether the cut portion was cut. This procedure was carried outon 50 bags in total.

A: No cut

B: Cut in one or two bags

C: Cut in three bags or more

(3) Total Evaluation

A: A for all of the items

B: one of B and the others of A

C: one or more of C

TABLE 1 Opening Dropped-Bag Total Feeling Breakage Resistance EvaluationExample 1 A B B Example 2 B A B Example 3 A A A Comparative 1 C B C

INDUSTRIAL APPLICABILITY

The invention is applicable as a packaging bag for packaging variousarticles such as foods, pharmaceutical and medical products, cosmeticsand groceries.

EXPLANATION OF CODES

-   -   1: packaging bag with a zipper tape    -   10: bag body    -   10A: inner surface    -   14: opening portion    -   15: containing space    -   20: zipper tape    -   21: male member    -   211: male belt-like base    -   22: female member    -   221: female belt-like base    -   23: engagement portion    -   31, 41: thick portion    -   32,42,52: cut portion    -   33: seal base

1. A zipper tape comprising: a pair of a male member and a female membercomprising: an engagement portion that is engageable and disengageableand defines a containing space inside a bag body; and belt-like basesthat are continuously connected to the engagement portion and arebondable to an inner surface of the bag body, wherein a first one of thebelt-like bases comprises: a thick portion that is formed thicker thanthe first one of the belt-like bases at an end near the containingspace; a cut portion that is continuously connected to the end of thethick portion near the containing space and is formed thinner than thefirst one of the belt-like bases; and a seal base that is continuouslyconnected to an end of the cut portion near the containing space, formedthicker than the first one of the belt-like bases, and attached to theinner surface of the bag body to which a second one of the belt-likebases is attached, wherein the thick portion is attached to the innersurface of the bag body to which the second one of the belt-like basesis attached by a strength lower than a strength for the seal base to beattached to the inner surface of the bag body, and the cut portion isprovided in a form of a belt spaced away from the inner surface of thebag body, the cut portion isolating the containing space from theoutside and having a strength lower than the strength for the seal baseto be attached to the inner surface of the bag body.
 2. The zipper tapeaccording to claim 1, wherein the thick portion and the seal base areformed substantially in the same thickness.
 3. The zipper tape accordingto claim 1, wherein, the thick portion is formed narrower toward theinner surface of the bag body.
 4. The zipper tape according to claim 3,wherein a surface of the thick portion and a surface of the seal basewhich face each other across the cut portion are substantially parallelto each other and are substantially orthogonal to the inner surface ofthe bag body to which the thick portion and the seal base are attached.5. A packaging bag with a zipper tape, comprising: a bag body having anopening portion for defining a containing space; and the zipper tapeaccording to claim 1, the zipper tape being provided on an inner surfaceof the bag body.